First off, look into the lemon law rules, I am not entirely sure what they entail. Them saying that they can't get a new engine is total BS. I was looking at RX-8's last weekend and the salesman was bragging about how they have the only certified RX-8 tech in the state (CO.) To become certified you have to totally disassemble and reassemble a new engine so that implies that they do in fact exist.
Call the regional Mazda rep and explain what happened, you would think they have had enough bad press on the RX-8 to be helpful at this point. You can probably get the number online somewhere, but it might be better to go into the dealer and ask for the number and when he might next be visiting the dealer
That should get someones attention.